Two rules matter most:
- If the user’s query is identical to an eligible Search keyword, Search is prioritized over Performance Max.
- If the query is not identical, PMax can compete, and the winner is often whichever has a higher Ad Rank.
So scaling without cannibalization is mainly about making sure your Search campaigns stay eligible and strong for the queries you care about, while you push PMax to find incremental volume elsewhere.
A Practical Scaling Framework That Keeps Search Safe
1) Build “Search Guardrails” Before You Increase PMax Budget
If Search is budget-limited or missing coverage, PMax will naturally fill the gap.
What to do:
- Lock down your money keywords in Search with exact match coverage for the highest intent queries you never want to lose (top services, top products, top converting themes). Because identical queries get prioritized to Search, this is your cleanest protection layer.
- Own your brand in Search intentionally. If you want Search to keep the brand, keep a dedicated brand campaign healthy and not constrained by budget.
- Watch “Search lost IS (budget)” and “Search lost IS (rank)” on your core campaigns. If either is high, fix that first. Otherwise, you scale PMax, and it will simply harvest what Search could not capture.
This step sounds basic, but it is usually the difference between “PMax scaling” and “PMax reshuffling.”
2) Use PMax Controls to Prevent Unwanted Query Overlap
PMax is not fully manual, but you do have levers now that are perfect for anti-cannibalization.
Brand exclusions
If you want PMax to stop chasing your brand queries, apply brand exclusions so it will not serve on those branded searches (this is specifically for Search and Shopping inventory).
This is one of the cleanest ways to keep brand performance reporting and efficiency stable, especially if you use brand Search for protection, messaging control, or reporting consistency.
Negative keywords
You can add campaign-level negative keywords (and also account-level negatives) to prevent PMax from showing on specific unwanted terms, again on Search and Shopping inventory.
Use negatives to block:
- Competitor names you do not want to pay for
- Low intent terms like “free”, “jobs”, “definition”, “pdf”, “template” (depends on your business)
- Irrelevant product variants or locations you do not serve
This is not about being aggressive with exclusions. It is about removing obvious waste, so the extra budget goes to new demand.
Search themes discipline
Search themes in PMax behave more like phrases and broad targeting, which means they can widen overlap if you are not careful.
If your goal is “scale without stealing,” keep themes focused on incremental categories, not the exact same clusters your Search campaigns already dominate.
3) Control Where PMax Sends Traffic (This Is a Hidden Cannibalization Fix)
A lot of “cannibalization” is actually landing page-driven. If PMax can auto-choose landing pages, it may route high-intent traffic to pages that compete with Search intent mapping.
Google recommends Final URL expansion for performance, but you can still control it by excluding URLs and tightening what pages are eligible. Practical approach:
Keep Final URL expansion on for reach, but exclude low-intent pages like blogs, careers, support pages, or broad category pages that confuse intent.
If you must keep strict routing, opt out of URL expansion and force only the pages you want.
This one change often reduces Search overlap because PMax stops “qualifying” for certain query intent patterns.
4) Scale Spend the Right Way (So You Do Not Reset Learning)
Once guardrails are in place, scaling is mostly about protecting stability.
A simple, field-tested pacing rule:
- Increase budgets in controlled steps (often 10 to 20 percent at a time), then hold long enough to let bidding re-stabilize before the next bump.
While you scale, track two things weekly:
- Search efficiency and volume on core non-brand campaigns (CPA or ROAS, plus impression share trends)
- PMax incrementality signals, especially whether it is expanding into new queries and new inventory, rather than just taking existing Search demand
How to Prove You Are Scaling Incrementally (Not Just Moving Conversions)
Use the visibility Google is adding around PMax performance to avoid guessing. Channel-level performance reporting and deeper insights are meant to show what is actually driving results.
A practical audit method:
- Compare PMax search term insights with your Search queries
- If overlap increases, tighten brand exclusions, negatives, themes, and landing page eligibility
- If Search impression share drops while total conversions stay flat, that is a red flag for substitution rather than growth
Common Mistakes That Cause Cannibalization While Scaling
- Scaling PMax while Search is budget-limited
- Letting brand queries flow into PMax unintentionally instead of choosing one “owner” campaign
- Using broad Search themes that mirror your best Search ad groups
- Allowing URL expansion to send traffic to pages that compete with your Search intent structure
- Making frequent large bid and budget changes that keep the system in constant re learning
Want a scaling plan that increases spend while keeping Search performance stable? Book a call with a Y77.ai performance expert, and we will map your guardrails, exclusions, and budget ramp plan to your exact account structure.
Book a free consultation with us.